“Water is our fuel” | The Press

Around twenty engineers, mathematicians and hydrometeorologists are gathered in a Hydro-Québec office in downtown Montreal. Everyone looks attentively at the weather maps which follow one another on a large screen. A specialist focuses for a moment on the amounts of precipitation expected in the coming hours near the La Grande-3 and La Grande-4 reservoirs, in Nord-du-Québec.

A little later, a meteorologist presents the weather conditions for the next week for each region of the province before giving the floor to a colleague who details the electricity demand from the day before, that coming from Quebec, but also that of outside the province.

This process repeats itself every morning. “It allows us to have a detailed portrait of the resource, because water is our fuel,” says water resources engineer Pierre-Marc Rondeau. However, the volume of fuel fluctuates considerably over the seasons and years.

As proof, due to low precipitation over the past two years, Hydro-Québec's 28 reservoirs are currently at their lowest level in 10 years. Result: for a rare time in 20 years, Hydro-Québec begins winter with a quantity of energy stored below 100 terawatt hours.

And it is to be able to accurately evaluate and predict the resources that will be available in its reservoirs that Hydro-Québec has developed complex calculation models capable of recreating the natural behavior of the water cycle.

“When there is precipitation, we integrate this data into mathematical models developed for each watershed,” explains Charles Mathieu, hydrometeorologist. “Mathematical equations allow us to reproduce the way in which water will flow to the reservoir by considering infiltration into the ground as a function of temperatures and the heat that can cause evaporation. »

The same goes for snow. “Snow is a form of reservoir because, in fact, it is water stored in another form,” indicates hydrometeorologist Alexandre Vidal. And the contribution of snow cover is appreciable; it actually represents nearly a third of what supplies Hydro-Québec's reservoirs.

“More extreme” changes

Until the beginning of the 21st century^e century, teams traveled the territory to take samples. Since then, Hydro-Québec has instead used a technology that measures the “water equivalent” of snow cover: GMONs. “Because what interests us is not so much the thickness of the layers of snow, but the quantity of water in the form of snow which covers the ground,” explains Mr. Vidal.

Around a hundred GMONs have been placed in strategic locations across the territory, both in the heart of dense coniferous forests and on open land. “It allows us to evaluate, when it melts, how quickly the snow transforms into water,” he says. The snow that covers an open area following logging, for example, will melt more quickly.

Subsequently, Hydro-Québec cross-checks the data that the GMONs transmit to it four times a day with information relating to the basins as well as meteorological, geographical and even geological information.

Hydro-Québec's ability to anticipate the volume of available resources is crucial in a context of climate change.

During the presentation of Hydro-Québec's results last summer, Executive Vice-President Strategy and Finance Maxime Aucoin argued that the company would have to juggle “greater volatility” in precipitation over the years. This is what emerges from studies carried out with the Quebec consortium on climate change Ouranos.

By the same token, the low hydraulicity recorded over the last two years cannot serve as an indicator of the trend for the coming years, maintained Mr. Aucoin: “When we look at the long-term forecasts, we see that the Climate change is not expected to reduce precipitation. In fact, it should even increase them slightly. »

“What our histories have taught us is that there are sequences of changes in hydrological regimes over the years,” explains Charles Mathieu. The 1960s were marked by “dry periods” while the following decade was characterized by “wet periods”. “The sequences extended over a few years, now the changes are more variable and more extreme,” he says.